1. Field of the Invention
The present invention relates to clamping circuits. More specifically, the present invention relates to radio frequency clamping circuits.
2. Description of the Related Art
Clamping circuits are used to protect electronic components, circuits and systems against excessive and potentially harmful currents and voltages. In radio frequency systems, for example, clamping circuits have been used to protect analog-to-digital (A/D) converters from over-voltages.
One conventional clamping approach involves the use of switches to isolate the protected circuit or circuit component from a deleterious source of excessively high energy. However, this approach requires a detector and therefore tends to be relatively expensive. In addition, it is difficult to achieve a sufficiently fast response time to provide adequate protection in many cases.
Accordingly, a preferred approach involves the use of diodes to shunt over-voltages to ground. However, the diode approaches known in the art have suffered from linearity problems. That is, these devices have often failed to accurately pass signals below a clamping threshold without degradation.
Accordingly, a need remains in the art for an improved system or method for protecting circuits, components and systems from excessive voltages and currents with good linearity and minimal expense.
The need in the art is addressed by the clamping circuit of the present invention. The inventive clamping circuit includes an input/output node, adapted to be coupled to a protected circuit or component; a first diode having an anode connected to the input/output node; a second diode having a cathode connected to the input/output node; a third diode connected between the cathode of the first diode and the anode of the second diode; a first arrangement for supplying a first potential at the cathode of the first diode to reverse-bias the first diode, while causing the third diode to go into conduction; a second arrangement for supplying a second potential at the anode of the second diode to reverse-bias the second diode, while causing the third diode to go into conduction; a first capacitor connected between the cathode of the first diode and ground; and a second capacitor connected between the anode of the second diode and ground.
In the illustrative embodiment, the anode of the third diode is connected to the cathode of the first diode, the first arrangement includes a first resistor connected between a first power supply and the cathode of the first diode, and the second arrangement includes a second resistor connected between a second power supply and the anode of the second diode. The illustrative embodiment further includes a third resistor connected between the cathode of the first diode and ground and a fourth resistor connected between the anode of the second diode and ground.